Tool holder for measurement means

ABSTRACT

The invention relates to a tool holder serving to receive measurement means ( 9, 10, 13 ) for characterizing a multi-phase fluid coming from a deposit ( 17 ) through which at least one well ( 16 ) passes, and flowing inside said tool holder. According to the invention, the tool holder is provided with an axial cavity ( 3 ) and with a first radial opening ( 4 ) which opens out in the inside wall of said tool holder and intercepts said axial cavity, said cavity and said opening serving to receive said measurement means. The invention also relates to a device for characterizing a multi-phase fluid coming from a deposit ( 17 ) through which at least one well ( 16 ) passes, said device comprising: a source unit ( 9 ) for emitting gamma rays through said multi-phase fluid, and a detector unit ( 10 ) having a scintillator crystal ( 10   a ) receiving said gamma rays after they have passed through the fluid. According to the invention, said device further comprises a tool holder ( 1 ) of the invention, and the detector unit ( 10 ) is positioned in the axial cavity ( 3 ) of said tool holder so that the scintillator crystal ( 10   a ) is situated in the first radial opening ( 4 ) in said tool holder.

[0001] The invention relates to a tool holder for measurement means, andmore particularly to a tool holder for receiving measurement meansmaking it possible to characterize a multi-phase fluid coming from adeposit through which at least one well passes. The invention alsorelates to a device for characterizing a multiphase fluid coming from adeposit, said device comprising a a tool holder of the invention andmeasurement means making it possible to determine the density and themulti-phase ratio of said fluid.

[0002] The capacity of the petroleum industry to optimize productionfrom a deposit is dependent on it being possible to evaluatecontinuously the quantity (flow rate) and the composition (proportionsof the various phases) of the effluent output from the well.Conventional practice in the petroleum industry for characterizing thecomposition of multi-phase effluents consists in separating the effluentinto its component phases, and in measuring the resulting separatedphases. But in that technique, separators must be put in place on site,and such equipment is costly and voluminous. And also, when doing welltesting, additional pipes must be put in place.

[0003] Numerous proposals have been put forward for developingtechniques that avoid the need for such separators. Such developmentsare described in Publication SPE 28515 (SPE Annual Technical Conference,New Orleans, Sep. 25-28, 1994) by J. Williams, entitled “Status ofMultiphase Flow Measurement Research”.

[0004] Among those solutions, it is known that a device can be used thatcomprises a source which emits gamma rays through the effluent in orderto determine its multi-phase ratio and its density, the attenuation ofsaid rays being measured by a detector unit situated facing the sourceunit. Document U.S. Pat. No. 5,361,632 describes a device forcharacterizing an effluent by using a gradiomanometer and a gamma raydensimeter. Unfortunately, that device is ineffective in wells that areclose to the horizontal In addition, since such a device obstructs thewell, it cannot be installed permanently.

[0005] Document PCT/GB00/01758 describes a device for measuring thedensity and the multi-phase ratio of the fluid. That device makes itpossible to obtain better results regardless of the types of welltested, and it is capable of being installed permanently down the well.That device comprises a tool holder constituting a segment of aproduction tube located down a well that passes through at least onedeposit of multi-phase fluid. That tool holder receives a gamma raysource unit and a detector unit. The source unit and the detector unitare installed on diametrically-opposite outside walls of the toolholder. The effluent to be characterized thus passes through the insideof the tool holder and it is intercepted by the beam of gamma rays sentby the source unit, and the attenuation of the rays is then measured bythe detector unit. In spite of it being ingenious, that device doessuffer from some drawbacks. Optimum accuracy is not obtained inmeasuring the attenuation of the gamma rays, in particular due to thepositioning of the source unit and of the detector unit. Since the unitsare installed on the outside walls of the tool holder, the gamma rayscoming from the source unit must firstly pass through the thickness ofthe tool holder—and they are therefore subjected to initial interferenceattenuation and then they must go back through said tool holder—therebybeing subjected to subsequent interference attenuation—in order to bedetected by the detector unit. The counts performed by the detector unitare thus disturbed significantly by the initial and subsequentinterference attenuation suffered by the gamma rays.

[0006] It would therefore be particularly advantageous to provide a toolholder in which the means for receiving the measurement means, inparticular for receiving a source unit and a detector unit, make itpossible to minimize the interference attenuation of the gamma rays.This can be achieved by bringing the source and the scintillator crystalof the detector directly closer to the inside walls of the tool, e.g. byinstalling them directly in contact with the flow of fluid to becharacterized However, numerous constraints must be satisfied by thetool holder, which must first and foremost be strong enough to withstandhigh pressures, in particular the differential pressure prevailingbetween the inside and the outside of the tool. The tool holder mustalso be leaktight because the multi-phase fluid flows through it, whilethe measurement tools must be connected to electronic means that conveythe data back to the surface, and that are generally situated on theoutside wall of said tool holder: there must not be any disturbance tothe flow rate desired for the multi-phase fluid at the surface;therefore there must not be any leaks between the outside and the insideof the tool holder.

[0007] An object of the invention is thus to provide a tool holder thatmakes it possible to improve the results obtained when characterizing amultiphase fluid, while still satisfying the conditions required by thestrength and sealing constraints, in particular when it is used down awell bored through geological formations.

[0008] To this end, the invention provides a tool holder serving toreceive measurement means for characterizing a multi-phase fluid comingfrom a deposit through which at least one well passes, and flowinginside said tool holder. According to the invention, the tool holder isprovided with an axial cavity and with a first radial opening whichopens out in the inside wall of said tool holder and intercepts saidaxial cavity, said cavity and said opening serving to receive saidmeasurement means.

[0009] In this way, the axial cavity makes it possible to receive partof the measurement tools without weakening the tool holder, and theradial opening makes it possible to bring the detection means of themeasurement tools closer to the effluent, and thus to reduceinterference attenuation generated by the disposition of the detectionmeans in state-of-the-art devices. In addition, the simplicity of theway in which the cavity and the openings are arranged makes it possiblefor the tool holder to be sealed simply and effectively. Finally, it isnot necessary to manufacture special tool holders in order to obtainthese advantageous effects, it being sufficient merely to modifyexisting tool holders, which limits the cost of the solution of theinvention.

[0010] In an advantageous embodiment of the invention, the tool holderis further provided with a second radial opening which opens out in theinside wall of the tool holder and is diametrically opposite from thefirst radial opening.

[0011] In particular when the measurement means include a source unitserving to send gamma rays through the effluent towards a detector unit,this solution makes it possible firstly to bring the detector unit(situated in the first radial opening) closer to said effluent, andsecondly to bring the source unit (situated in the second radialopening) closer to said effluent. In this way, in combination with theradial opening receiving the detector unit, the tool holder of theinvention makes it possible to reduce all of the interferenceattenuation due to the walls of state-of-the-art tool holders.

[0012] In a preferred embodiment of the invention, the first radialopening also opens out in the outside wall of the tool holder, and it issealed off by a stopper situated on said outside wall.

[0013] In this embodiment, the radial opening is formed merely by radialboring from the outside wall of the tool holder. This embodiment ispreferred because the machining it requires is very practical andinexpensive. In which case, in order to make the tool holder leaktight,it is necessary merely to place a stopper on its outside wall.

[0014] The invention also provides a device for characterizing amulti-phase fluid coming from a deposit through which at least one wellpasses, said device comprising:

[0015] a source unit for emitting gamma rays through said multi-phasefluid; and

[0016] a detector unit having a scintillator crystal.

[0017] According to the invention, the characterizing device furthercomprises a tool holder as proposed above, and the detector unit ispositioned in the axial cavity of said tool holder so that thescintillator crystal is situated in the first radial opening in saidtool holder.

[0018] Advantageously, the first radial opening is an oblong openingwhose dimensions correspond to the dimensions of the scintillatorcrystal. This makes it possible for the bores in the tool holder to be“just large enough.” Thus, the results delivered by the measurementmeans are optimized—it is particularly important for the crystal to bedirectly in contact with the fluid to be characterized—while minimizingthe weakening of the tool holder, in order to guarantee the strengththereof.

[0019] Other advantages and characteristics of the invention arehighlighted in the following description given with reference to theaccompanying drawings, in which:

[0020]FIGS. 1a and 1 b-are section-views of an embodiment of a toolholder of the invention;

[0021]FIG. 1c is a section view of another embodiment of a tool holderof the invention;

[0022]FIG. 2 is a section view of an embodiment of a device of theinvention for characterizing a fluid;

[0023]FIG. 2a is a detail of an embodiment of a device of the inventionfor characterizing a fluid; and

[0024]FIG. 3 is an example of the use of a device for characterizing afluid as shown in FIG. 2.

[0025]FIGS. 1a and 1 c show two embodiments of a tool holder 1 of theinvention. As can be seen in FIG. 1b which shows a section through theembodiment shown in FIG. 1a, the body of the tool holder 1 issubstantially cylindrical in shape with, over a portion of its length,an eccentric segment 2, i.e. a portion in which the outside diameter D,of the tool holder 1 is greater than the outside diameter D of theremainder of said tool holder, while the inside diameters remainidentical. The eccentric segment is also present in the embodiment shownin FIG. 1c. However, this shape is not limiting to the invention, andthe tool holder may have any shape suitable for receiving measurementmeans.

[0026] The eccentric segment 2 is provided with an axial cavity 3 oversubstantially its entire length. The axial cavity 3 is preferablyprovided where the thickness of the eccentric segment 2 is greatest, inorder to minimize weakening the body of the tool holder. But as can beseen in FIG. 1b, depending on the conditions under which the tool holderis used, the axial cavity 3 may be provided in any thickness of theeccentric segment provided that its dimensions are suitable for ensuringthat the tool holder retains sufficient strength. Since the cavity 3extends along the entire length of the eccentric segment 2, its endwhich is opposite from the end receiving the measurement means is sealedoff by sealing means 3 a known in the state of the art.

[0027] The diameter of the axial cavity is dimensioned so as to minimizethe extent to which it weakens the eccentric segment 2 of the toolholder, while making it possible to receive measurement means of usualdimensions, and whose diameter is referenced D₂. The dimensions of thecavity depend firstly on the material from which the tool holder is madeand secondly on the technique used for subsequent insertion of themeasurement means, in particular of the detector unit, as explainedbelow with reference to FIG. 2. There are two possible ways ofinstalling said means:

[0028] the measurement means are inserted from the outside of the toolholder, as in the embodiment shown in FIGS. 1a and 1 b; or

[0029] the measurement means are inserted from the inside of the toolholder, as in the embodiment shown in FIG. 1c.

[0030] With reference to FIGS. 1a and 1 b:

[0031] The diameter of the axial cavity is totally contained within thethickness of the eccentric segment 2. Therefore, in order to positionthe measurement means in contact with the fluid flowing through the bodyof the tool holder, it is necessary to form a first radial opening 4 inthe inside wall of the tool holder, and intercepting the axial cavity 3.A second radial opening 5 opens out into the inside wall of the toolholder, diametrically opposite from the first radial opening 4. Asexplained in more detail with reference to FIG. 2, the two radialopenings make it possible to install a gamma ray source and ascintillator crystal of a detector unit so that they face each other inorder to characterize a fluid flowing through the tool holder. The factthat the openings 4 and 5 open out in the inside wall of the tool holderthus makes it possible to bring the measurement means closer to thefluid to be characterized, and thus to minimize all of the interferenceattenuation that is generated by tool holders in the state of the art.

[0032] Advantageously, a window made of materials that offer low gammaray attenuation (e.g. poly-ether-ether-ketone (PEEK), a thermoplasticresin) may be provided in the inside wall of the tool holder at each ofthe radial openings 4 and 5. Such a window makes it possible to avoidany fluid or debris stagnating in the space extending between the insidewall of the tool holder and the walls of the measurement means. In theembodiment of the invention, the radial openings 4 and 5 are formedmerely by radial boring from the outside wall of the tool holder. Thissolution is advantageous because it is very easy and thereforeinexpensive to achieve. In which case, in order to guarantee that thetool holder is leaktight, leaktight stoppers 6 and 7 are providedrespectively for the radial opening 4 and for the radial opening 5. Theradial openings 4 and 5 may also be formed by tools inserted inside thetool holder 1. In which case, said radial openings do not open out inthe outside wall of said tool holder, and it is not necessary to providestoppers 6 and 7. However, this solution requires machining that is morecomplex.

[0033] The solution shown with reference to FIGS. 1a and 1 b istherefore advantageous not only because it is particularly easy toinstall the measurement means from the outside of the tool holder, butalso because said means are then easily accessible, and they aretherefore easy to remove for the purposes of repair or the like.However, since it requires a radial opening 4 to be bored thatintercepts the axial cavity 3, this solution weakens the tool holder.Thus, the diameter of the axial cavity must be relatively small, and,consequently, the diameter D₂ of the measurement means must be smaller.Strength tests were performed for a tool holder made of a standardmaterial whose strength was 550 megapascals (MPa) (=80,000 pounds persquare inch (psi)), and whose eccentric segment diameter D₁ was about148.6 millimeters (mm) (=5.85 inches (″)), under conditions close tothose which apply to a tool holder when used down a well that passesthrough at least one deposit of fluid, namely: differential pressurebetween the inside and the outside of the tool holder of about 40 MPa(6,000 psi), and hydrostatic pressure of the fluid flowing through thetool holder of about 103 MPa (15,000 psi). Under those conditions, thetests show that good tool holder strength is obtained for a diameter D₂of the measurement means of about 31.8 mm (1.25″) when the axial cavity3 is not bored where the thickness of the eccentric segment 2 is at itsmaximum, but rather it is offset at an angle of about 300, as shown inFIG. 1b, this offset being to make it simpler to install the measurementmeans, as explained in more detail with reference to FIG. 2. Under suchconditions, the length of the oblong radial bore 4 was about 140 mm,which corresponds to the standard length of a scintillator crystal of agamma ray detector unit. Naturally, depending on the material and on thegeometrical characteristics of the tool holder, the dimensions of themeasurement means, and thus of the cavity and the openings, may bemodified insofar as the tool holder is strong enough to withstand theconditions of use that prevail down an oil well.

[0034] With Reference to FIG. 1c:

[0035] The embodiment shown in FIG. 1c is identical in its principle tothe embodiment shown in FIGS. 1a and 1 b, and it thus makes it possibleto bring the measurement means closer to the fluid flowing through thebody of the tool holder, in order to reduce the noise that interfereswith measurements obtained with tool holders known from the state of theart.

[0036] However, in this case, the measurement means are not insertedfrom the outside of the tool holder, but rather they are inserted frominside said tool holder. This solution suffers from the drawbacks ofmaking it more difficult to access the measurement means and moreawkward to install them because an installation tool must be used to putthe measurement means into the body of the tool holder 1, and then toposition them in the axial cavity 3. In this embodiment, the measurementmeans are installed tangentially to the inside diameter of the toolholder. An axial cavity 3 is bored that is of diameter smaller than thediameter of the axial cavity 3 in the solution described with referenceto FIGS. 1a and 1 b. However, since the measurement means are broughteven closer to the fluid to be characterized, it is possible to increasethe diameter D₂ of said means. It is also possible to increasesignificantly the dimensions of the radial opening 4. This results in alarger area in contact with the fluid, and thus in the possibility ofusing detection means that are larger (and therefore more accurate).This solution does not weaken the tool holder. Indeed, placing themeasurement means in the tool holder makes it possible to increase thethickness of the stopper 6 (when the radial opening 4 is bored from theoutside wall of the tool holder) and thus to increase the overallstrength. Thus, tests performed under the same conditions as thosedescribed above with reference to FIGS. 1a and 1 b have shown that thestrength of the tool holder is satisfactory for measurement means havinga diameter D₂ of about 35 mm (1.37″) bored at about 300 from the maximumthickness of the eccentric segment 2.

[0037] In the same way as in the preceding embodiment, a radial opening5 is bored diametrically opposite the axial cavity 3, said radialopenings serving in particular for receiving the source of a sourceunit, as explained below. A stopper 7 may be positioned over the radialopening 5, and windows made of a material offering low gamma rayattenuation may be installed on the inside wall of the tool holder,closing the openings 4 and 5.

[0038] A measurement device 8 of the invention is described in detailbelow, with reference to FIGS. 2 and 2a, said device being provided witha tool holder as in the embodiment shown in FIGS. 1a and 1 b.

[0039] The body of the measurement device, which body is constituted bya tool holder of the invention, constitutes a segment of tubing lowereddown into a well that passes through at least one deposit of fluid to becharacterized, said fluid flowing inside said tubing. As shown in FIG.2, the measurement device 8 makes it possible to characterize thedensity and the multi-phase ratio of the fluid coining from the deposit,said fluid usually being constituted by water, hydrocarbons, and gas.For this purpose, the tool holder 1 of the device 8 receives a sourceunit 9 making it possible to send gamma rays through the fluid, and adetector unit 10 comprising firstly a scintillator crystal 10 a formeasuring the attenuation of the rays after they have passed through thefluid, and secondly an acquisition unit 10 b for processing the countsignal transmitted by the scintillator crystal.

[0040] As shown in detail in FIG. 2a, the source unit 9 is receivedentirely in the radial opening 5 which opens out in the inside wall ofthe tool holder 1. Thus, the source emitting the gamma rays is directlyin contact with the multi-phase fluid, which considerably reduces theattenuation of the rays on emission. In addition, this configurationmakes it easy to install the source unit 9 in the opening 5 from theoutside of the tool holder. Finally, when the multi-phase fluid alsoflows between the walls of the well and the outside walls of the toolholder without going through the device of the invention, sealingbetween the inside and the outside of the tool holder is provided, e.g.by welding the stopper 7 of the source unit in the opening 5, which isvery easy and inexpensive.

[0041] The detector unit 10 is received facing the source unit 9. Inpractice, the acquisition unit 10 b is received in the axial cavity 3,as is the scintillator crystal 10 a. Said crystal is further situatedwhere the first radial opening 4 intercepts said axial cavity. In thisway, the scintillator crystal is also in direct contact with the fluidto be characterized, and it receives the gamma rays after attenuation,with interference attenuation being minimized.

[0042] As shown in FIG. 2, electronic communications and power supplymeans 11 situated on the outside wall of the tool holder 1, outside theeccentric segment 2, are connected to the acquisition unit 10 b. Sincethe position of the electronic means 11 on the outside wall of the toolholder 1 is induced by the position of relay elements (not shown) alongthe other segments of the tubing, said electronic means 11 can findthemselves offset relative to the maximum thickness of the eccentricsegment 2, as is shown in FIG. 2. As a result, in order to position thedetector unit in alignment with the electronic means, the axial cavityis not bored in the maximum thickness of the eccentric segment 2, butrather it is offset therefrom, as described above, by an angle of about30°. Naturally, it is possible to consider having an angular offsetbetween the axial cavity and the position of the electronic means, inparticular, for example, so as to bore said cavity in the maximumthickness of the eccentric segment. Such an offset would make itpossible to increase the diameter of the axial cavity 3. Tests conductedunder the same conditions as those described above have shown that it ispossible to obtain good tool holder strength for a diameter D₂ that isslightly greater than 31.8 mm for the embodiment shown in FIGS. 1a and 1b and about 36 mm for the embodiment shown in FIG. 1c.

[0043] Such a configuration would however assume that the link means 12between the detector unit and the electronic means are provided withbends, which would complicate installing the measurement device 8. It is13 also necessary to seal said link. Thus, when the electronic means 11are in alignment with the detector unit 10, the link 12 can be sealedmerely by means of a sealed single metal/metal connection with conicalcontact at the electronic means, and by annular gaskets at the axialcavity 3. In contrast, an angular offset between the detector unit andthe electronic means, requiring link means 12 provided with bends, wouldmake it necessary for two metal/metal connections to be present in orderto provide overall sealing: both at the detector unit end and at theelectronic means end. For this purpose, the positioning of the detectorunit 10 in alignment with the electronic means 11 is preferred.

[0044] Finally, in the embodiment shown in FIG. 2, the measurementdevice 8 further comprises means for mixing the phases of the fluid, sothat the measurement means for measuring the density and the multi-phaseratio operate properly. In an advantageous embodiment, these mixingmeans also make it possible to measure the flow rate of the multi-phasefluid. For this purpose, the device comprises in particular pressuresensors (known and not shown for reasons of clarity), and a venturi 13positioned inside the tool holder 1 by means of a fastening device 14known from the sate of the art. In which case, it is the venturi 13which performs the function of mixing the phases of the multi-phasefluid. As can be seen in FIG. 2, it is important for the fasteningdevice 14 to be dimensioned and/or positioned so that it is not extendedto the point of being placed between the source unit 9 and thescintillator crystal 10 a, which would result in losing the advantage ofpositioning these two elements directly in contact with the fluid. Inthe embodiment of the tool holder of FIG. 1c, where the contact areabetween the scintillator crystal and the fluid is larger, it isnecessary to make provision for cutouts to be formed in the fasteningdevice so that the source unit and the crystal can face each otherunobstructed. This makes the embodiment shown in FIG. 1c less practicalthan the embodiment of FIGS. 1a and 1 b because it is particularlydifficult to position such cutouts and openings correctly (since themanipulation is performed from the surface).

[0045] Naturally, in order to enable other measurement means to belowered down inside the tubing of which the device 8 constitutes asegment, the measurement means for 6 measuring the flow rate can beeasily removed using techniques known from the state of the art.

[0046]FIG. 3 shows an embodiment of a measurement device 8 of theinvention. Tubing 15 is lowered down a well 16 passing through at leastone petroleum deposit 17. The tubing 15 is made up of a plurality ofsegments, one of which is constituted by the measurement device 8. Thefluid coming from the deposit 17 penetrates into the device 8 asindicated by the arrows F, and the above-described measurement meansmake it possible to determine its density and/or its flow rate. Thesimplicity of the measurement device of the invention and thepossibility of accessing the measurement means as a result of theirconfiguration in the tool holder makes it possible to install saiddevice permanently down the well, with maintenance posing no particularproblem.

1/ A tool holder serving to receive measurement means (9, 10, 13) forcharacterizing a multi-phase fluid coming from a deposit (17) throughwhich at least one well (16) passes, and flowing inside said toolholder, said tool holder being characterized in that it is provided withan axial cavity (3) and with a first radial opening (4) which opens outin the inside wall of said tool holder (1) and intercepts said axialcavity, said cavity and said opening serving to receive said measurementmeans. 2/ A tool holder according to claim 1, characterized in that itis further provided with a second radial opening (5) which opens out inthe inside wall of the tool holder (1) and is diametrically oppositefrom the first radial opening (4). 3/ A tool holder according to claim 1or 2, characterized in that the first radial opening (4) also opens outin the outside wall of the tool holder (1), and is sealed off by astopper (6) situated on said outside wall. 4/ A tool holder according toany preceding claim, characterized in that its outside wall serves toreceive electronic communications and power supply means (11) connectedto the measurement means. 5/ A tool holder according to any precedingclaim, characterized in that it is in cylindrical in shape with aportion of the length of the cylinder being provided with an eccentricsegment (2) in which the axial cavity (3) and the first radial opening(4) are bored. 6/ A device for characterizing a multi-phase fluid comingfrom a deposit (17) through which at least one well (16) passes, saiddevice comprising: a source unit (9) for emitting gamma rays throughsaid multi-phase fluid; and a detector unit (10) having a scintillatorcrystal (10 a) receiving said gamma rays after they have passed throughthe fluid; said device (8) being characterized in that it furthercomprises a tool holder (1) according to any preceding claim, and inthat the detector unit (10) is positioned in the axial cavity (3) ofsaid tool holder so that the scintillator crystal (10 a) is situated inthe first radial opening (4) in said tool holder. 7/ A tool holderaccording to any preceding claim, characterized in that the first radialopening (4) is an oblong opening whose dimensions correspond to thedimensions of the scintillator crystal (10 a). 8/ A device according toclaim 7 and claim 2, characterized in that the source unit (9) issituated in the second radial opening (5) in the tool holder (1). 9/ Adevice according to claim 7 or 8, characterized in that it furthercomprises means (13, 14) for determining the flow rate of themulti-phase fluid, said means being fixed to the tool holder (1)upstream from the detector unit (10) and from the source unit (9). 10/ Adevice according to any one of claims 7 to 9, characterized in that itconstitutes a segment of tubing (15) that is lowered and fixedpermanently down the well (16) passing through the deposit (17) ofmulti-phase fluid.